Orient local axis to match mesh's shape
You may add a custom transform orientation based on your object's current orientation. In your case select the object in Object Mode, press Ctrl+Alt+Spacebar (or click a '+' button in a Transform Orientations panel of the Properties Shelf (N). It'll add a new orientation according to your object's position.


If you have more complicated object with the normals facing in different directions you may select the face/faces with desired angle/angles in Edit Mode and then press the buttons mentioned above. It'll orient the 3d gizmo according to the faces' position.


The newly added orientations (you may add as many as you like) are available in the Transform Orientation tab at the bottom bar of the 3D window.